| Soybean aphid,Aphis glycines,is an important pest of soybean,Glycine max,which often causes damage to soybean in the serious occurring years.The global climate is getting warmer in recent years.The environmental temperature is also getting warmer and extreme hot weather often occur in Harbin,China.To make clear the environmental warming effects,studies on effects of high temperature on the development and morph differentiation of A.glycines were studied.Apterous viviparous A.glycines were reared and the following three trials were conducted:(1)Soybean aphids were reared at constant temperatures 25,27,29,31,33,35 and 37±1℃,photoperiod 14L:10D and relative humidity 70±5%;effects of constant high temperature on development and reproduction of A.glycines were conducted.(2)Soybean aphids were reared at day temperatures 25,27,29,31,33,35 and 37±1℃,with night temperature 20±1℃,photoperiod 14L:10D and relative humidity 70±5%;effects of high day temperature on development and reproduction of A.glycines were conducted.(3)1)When A.glycines developed into the first,second,third and fourth instar and adult,they were exposed to a short-term high temperature for 7 days,respectively,with day temperature 3 5℃ and night temperature 20℃.Then they were reared at day temperature 25℃ and night temperature 20℃ and their development and reproduction were studied.2)The third instar of A.glycines were reared at day temperature 35℃ and night temperature 20℃ for 7 days,then development and production of their offspring reared at day temperature 25℃ and night temperature 20℃ were studied,from the 1st to the 5th generation.3)Gynoparae and males of A.glycines were induced in the laboratory at 20±1℃ and 10L:14D photoperiod.During this inducing period,the 1st to 4th instar and the adults were exposed to the day temperature of 3 5±1℃ for 7 days,respectively,with night temperature 20±1℃.Then the difference in inducing rate of A.glycines gynoparae and males were studied.By results of the trials mentioned above,effects of short-term high temperature on autumnal morph differentiation of A.glycines were studied.The conclusions were as follows:(1)Soybean aphid survived,developed and reproduced well at constant temperature range of 25 to 31℃.Development and reproduction of A.glycines were affected significantly by constant high temperature above 33℃.At 33℃,adult lifespan of A.glycines was only 4.11±0.39 days,which was significantly shorter than those at 25,27,29 and 31℃.Intrinsic rate of increase of A.glycines was-0.3695±0.1048 day-1 at 33℃,which was significantly smaller than those at 25 to 31℃.At 35℃,survival rate of A.glycines nymph was 4%.Only two nymphs could develop into adults,and they both were dead within 6 days.At 37℃,A.glycines nymph only survived for 4 days and could not develop into adult.At 33℃ and 35℃,body sizes of A.glycines adult were smaller.(2)Soybean aphid survived,developed and reproduced well at day temperature range of 25 to 33℃ with night temperature 20℃.Development and reproduction of A.glycines were affected significantly by day temperature above 35℃ with night temperature 20℃.At day temperature 35℃(20℃ at night),adult lifespan and adult fecundity of A.glycines were 6.00±0.66 days and 0.17±0.11 nymphs per female;these data were both significantly smaller than those at 25,27,29,31 and 33℃.At day temperature 35℃(20℃ at night),intrinsic rate of increase of A.glycines was-0.1957±0.0528 day-1,which was significantly smaller than those at 25 to 33℃.At day temperature 37℃(20℃ at night),A.glycines nymphs could not develop into adults and they all were dead within 4 days.At day temperature 35℃(20℃ at night),body size of A.glycines adult was significantly smaller than those at day temperature 25 to 33℃.(3)1)Development and reproduction of A.glycines were affected significantly when the third instar were exposed to a short-term high temperature.When the third instar were reared at day temperature 35℃(20℃ at night)for 7 days,survival rate of adults decreased to 34%in 10 days and nymph stage duration was shorter than those of the first instar,the second instar and adults.Intrinsic rate of increase of the third instar,exposed to day temperature 35℃ for 7 days,was as big as those of the first and second instar,but it was smaller than those of the fourth instar and adult.2)When the third instar of A.glycines were exposed to a short-term high temperature,survival rate of adult in the first generation decreased to 82%.Survival rate of adult returned to normal after the 2nd generation and those from the 2nd to 5th generation were all above 98%.When the third instar of A.glycines were exposed to a short-term high temperature,nymph stage duration of A.glyines in the first generation was shorter and the adult fecundity was smaller.After the 2nd generation,nymph stage duration and adult fecundity returned to normal.There were no significant differences in adult lifespan of A.glycines among different generations and between short-term high temperature and normal temperature.When the third instar of A.glycines were exposed to a short-term high temperature,intrinsic rate of increase of the first generation decreased,but they increased at the 2nd generation and was bigger than the normal temperature treatment.Body size of adult from the first generation became smaller,then they returned to normal after the 2nd generation,which was as big as or bigger than that at normal temperature.3)When A.glycines from the G1 generation were exposed to a short-term high temperature for 7 days from the first,second,third and fourth stadium or adult stage,occurring percentage of wingless virginoparae and gynoparae in the 1st day in G2 generation were both as same as that at normal temperature treatment.When A.glycines from the G1 generation were exposed to a short-term high temperature for 7 days from different nymph stage and adult stage,percentage of wingless virginoparae occurred in the 6th day in G2 generation is higher,but gynoparae percentage was lower than that at normal temperature.When A.glycines from the G1 generation were exposed to a short-term high temperature for 7 days from different nymph stage and adult stage,percentage of wingless virginoparae occurred in the 11th day in G2 generation is higher,but percentage of gynoparae and male is both lower than that at normal temperature.Our results provided important data for basic biological research on A.glycines.These data on life parameters of A.glycines at high temperatures were also important for forecasting dynamics of A.glycines in regions where the climate is getting warmer. |
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